Thanks for the replies. I did some more searching and found my owners manual, or what was given to me as the manual for the PHD. At the time of the purchase the PHD was just a model 301 it appears, which is now called the "Mole", I thought it was a "Mouse" based on the short auger bit. In my manual it says to use SAE 90 EP oil and to replace it after the first 50 hours of use. I don't think I have that many hours on it yet, probably closer to 10-20 so I will just top it off for now and use it some, then replace the oil. I have a lot of holes to dig in some pretty hard Atlanta area clay. My one man hand held auger didn't cut in more than about 12" on the softest spot I happened to try and just about wrenched my shoulders out of place doing that, so I am hoping this will be my saviour since digging by hand is too slow and way too much work in this 95 degree heat.
And if any of you have some advice on another aspect of this project I would appreciate your experience and wisdom for it. My existing auger bit is a 9" but most of the posts I want to put in will be 4x4 pressure treated. I do plan on using 6x6 posts at certain intervals, corners, potential gates, etc. where the 9" auger seems fine. However that size auger really leaves a big hole for a 4x4 so I bought a 6" bit at a nearby TSC store that is made for a different PHD. This 6" bit is too long for my tractor/PHD combination, and the attachment point seems to be a larger diameter than my Shaver gear box output shaft. On this new auger bit the attachment point is a larger pipe welded onto the shaft and the shaft appears to be the same diameter as the original Shaver shaft which directly mounts to its gear box shaft. So my plan is to cut off the oversized pipe section and drill the needed holes into the shaft to attach it to my Shaver.
What I don't know is if the shaft on the 6" bit is as heavy a gauge as the Shaver bit so it may not hold up too well. I also may need to cut off a few inches at the top of the fluting for good clearance between it and the safety shield/gear box. If the shaft is thin material then it no doubt will tear up quickly but I can't determine that without drilling a hole through it making it impossible to return the bit to the TSC store for a refund. Any advice on this plan is welcome.